The immune system recognizes pathogens, including viruses, by means of pattern recognition receptors (PRRs). Among the PRRs is the family of toll-like receptors (TLRs), RIG-like helicases (RLHs) as well as nucleotide-binding domain- and leucine-rich repeat-containing molecules (NLRs). Activation of PRRs leads to the activation of immune cells including dendritic cells (DCs) and the induction of innate and adaptive immune responses.
The development of new viral-based vaccines requires viral strains which exhibit a unique combination of characteristics. First, the virus used as a delivery vector in the vaccine is generally engineered, at the level of its genome, to comprise the coding sequence of one or more foreign antigens (a protein not expressed by the wild-type virus) against which an immune response is desired. In its expressed form, the foreign antigen presented to the subject to be immunized is generally a protein of the pathogen that causes the disease which vaccination is intended to treat or prevent. However, the foreign antigen can also be a host antigen, such as a tumor antigen. Upon delivery into target cells within the individual to be vaccinated, the sequence encoding the foreign antigen is expressed as the corresponding protein, and this protein then is recognized by the individual's immune system, which then mounts the desired immune response against the foreign antigen, enhancing the host's ability to specifically combat the disease caused by the pathogen from which the foreign antigen was taken. This intended mode of action means that viral strains suitable for use in vector vaccination strategies against a heterologous pathogen must retain their ability to infect host cells. At the same time, however, such viral strains should be attenuated in their own replicative behavior, so that they do not themselves replicate within the individual's host cell. They should also themselves be non-pathogenic.
A virus which has been engineered to comprise the coding sequence of a foreign antigen of interest, but which is not attenuated in its replication and/or pathogenicity may cause significant disease, possibly undermining the intended vaccination strategy. Therefore, the vector vaccine should be as attenuated as possible to prevent induction of disease and limit severe adverse effects. A virus which is attenuated in its own replication and/or pathogenicity, but which is not sufficiently immunogenic may deliver the sequence encoding the foreign antigen of choice to the individual's immune system, but is not likely to engender the desired immunogenic response against this antigen, thereby once again undermining the effectiveness of the vaccination strategy. Thus, the vaccine must elicit production of enough of the foreign antigen(s) to present to the host immune system so that the desired immune response is triggered. In addition, the vaccine must not suppress the host's immune system to induce a fast and highly effective immune response. At the same time, the host immune system must also itself be sensitive enough to react to the amount of foreign antigen produced by the vaccine.
The vaccinia virus K4L gene encodes a DNA nicking-joining enzyme (Eckert et al. 2005). Eckert et al. found that there were no significant differences between a wild-type vaccinia virus (Western Reserve, WR) and a corresponding vaccinia virus lacking K4L with respect to infectivity, growth characteristics, or processing of viral replicative intermediate DNA, including both telomeric and cross-linked forms.
The vaccinia virus B19R gene described in Symons et al. 1995 encodes a protein binding type I interferons (IFN-alphas/betas), thus neutralizing the biological activity of these type I interferons. All genes of vaccinia virus WR (VACV) mentioned in this report are designated using the names of their orthologue in the VACV strain Copenhagen (VACV-Cop) according to the VACV-Cop gene notation system (Rosel et al. 1986; Goebel et al. 1990). This also applies to VACV-WR genes that are referred to in the literature applying the nomenclature system now reserved for VACV-Cop orthologues due to strain variations in gene content and topology. For example, the gene encoding the VACV interferon type I-biding protein has historically been named B18R in the VACV-WR strain. The orthologue of this gene in the VACV-Cop is named B19R, and we thus refer to this gene as B19R in this application.
It is thus an object of the present invention to provide improved vaccines and vaccination strategies. It is a further object of the invention to provide treatment strategies for various diseases which are caused by excessive interferon and cytokine induction due to aberrant stimulation of TLR9 or other DNA recognition molecules of the innate immune system.